Polymerization process having improved alkyl boron initiators for ethylenically unsaturated compounds



United States Patent 3 413,274 POLYMERIZATION PR OCESS HAVING IMPROVEDALKYL BORON INITIATORS FOR ETHYLENI- CALLY UNSATURATED COMPOUNDS HiroshiWatanabe, Kamakura, Kinsuke Kato, Zushi, Shinji Ito, Kamakura, andHitoshi Murozono and Toshi Nakakaki, Yokohama, Japan, assignors to ToyoKoatsu Industries, Inc., Tokyo, Japan, a corporation of Japan NoDrawing. Filed Aug. 20, 1965, Ser. No. 481,405 Claims priority,application Japan, Aug. 22, 1964, 39/ 46,798 13 Claims. (Cl. 26087.3)

ABSTRACT OF DISCLOSURE This invention relates to methods of polymerizingethylenically unsaturated compounds.

In the polymerization of ethylenically unsaturated compounds, there hasalready been suggested a polymerizing method wherein an alkyl boron isused as one of -the two components forming a polymerization initiatortogether with hydrogen peroxide or oxygen. For example, it is known topolymerize vinyl compounds by using triethyl boron and hydrogen peroxidetogether or by using tri nbutyl boron and oxygen together.

As a result of researches with a view to improving the efficiency ofalkyl borons as polymerizing initiators, we have discovered thatethylenically unsaturated compounds can be very effectively polymerizedby using all three components of (1) a boron compound as hereinafterdescribed by general formula; (2) oxygen; and (3) hydrogen peroxide;together as the polymerization initiator at a rate of 0.001 to 1.0% byweight of said boron compound to the ethylenically unsaturated compoundand molar ratios of oxygen, said boron compound of 0.15/ .1 to 0.7/1 andof hydrogen peroxide, said boron compound of more than 03/1 to form thepolymerization initiator.

In the polymerization of ethylenically unsaturated compounds, accordingto our researches, as is evident also from the examples hereinafterpresented, we have made the following findings:

(1) When said boron compound is used alone in the absence of oxygen,substantially no polymerization will occur,

(2) When said boron compound and hydrogen peroxide are used together asin the above-mentioned conventional method, the polymerization 'velocitywill be low and (3) When said boron compound and oxygen are usedtogether as in the above-mentioned conventional method, thepolymerization velocity will rise more than in case (2) above andtherefore the yield of a polymer after the lapse of a fixed time willrise but still not to a satisfactory degree.

In either of the above-mentioned cases (2) and 3), if the amount of useof the boron compound is largely increased, it will be possible toincrease the polymerization velocity. However, in such case, the alkylboron and its intermediate reaction product will remain in the producedpolymer and the polymer will develop the very unpleasant odor of thealkyl boron and when heated, as in processin' the unpleasant odorbecomes unbearable. Furthermore, such alkyl borons are toxic to humanbeings and it is necessary to specifically refine the produced polymerto reduce Patented Nov. 26, 1968 the amount of alkyl boron compoundcontained thereby. It is presumed that, when an alkyl boron is oxidizedwith oxygen or hydrogen peroxide in the presence of an ethylenicallyunsaturated compound, the boron atom in the alkyl boron will convert toboric acid and it is thought that various organic compounds in which atleast one alkyl radical is directly bonded to a boron atom will also beproduced intermediately. The intermediate reaction product mentionedabove includes such compounds which are thought to be responsible, atleast in part, for the unpleasant odors described above.

As compared with the use of the respective polymerization initiators ineach of the above-mentioned cases (1), (2) and (3), the presentinvention, wherein the three components of the above-mentioned boroncompound, oxygen and hydrogen peroxide are used together in theabove-mentioned proportions, even if only a small amount of the boroncompound is used, the reaction velocity will be seen to increasesurprisingly, the yield of a polymer will increase remarkably and theproduced polymer will have no unpleasant odor as is described above. Norefining step is required and the industrial importance of the presentinvention is very high.

In the present invention, the mechanism by which the boron compound,oxygen and hydrogen peroxide perform is not clear. However, from thefacts that, if oxygen or hydrogen peroxide is not used with the boroncompound, no excellent results will be obtained and that differentpolymerization velocities result in the use of oxygen as compared to H 0it may be presumed that oxygen and hydrogen peroxide react with theabove-mentioned boron compound by respectively different mechanisms toproduce different free radicals.

In the method of the present invention, it is also evident that theabove-mentioned boron compound is more fully utilized while obtaining ahigh reaction 'velocity and yield of polymer and it is possible toreducethe amount of alkyl boron or its intermediate reaction product remainingin the polymeric product. It is furthermore probable that the boroncompounds substantially completely react to finally convert the boronatoms of the boron compounds to boric acid, thus explaining the absenceof runpleasant odors. According to the present invention, as comparedwith the known methods described above, even if the amount of the boroncompound used is reduced, a sufiicient reaction velocity still isobtained and considerable economic advantages result. Also, there are nodisadvantages as described above due to the boron compound or itsintermediate remaining in the resulting polymer.

The al-kyl boron compound used in the present invention is representedby the formula:

wherein Q is R CR or a halogen radical, i.e., chlorine, bromine, iodineand the like, and R R R and R are alkyl radicals and R is an alkylradical or hydrogen radical.

It is preferred here in practice that R R R and R4, are alkyl radicalsof 1 to 12 carbon atoms each and R is an alkyl radical of 1 to 12 carbonatoms or hydrogen. Typical examples of the abovementioned boroncompounds are triethyl boron, tri n-butyl boron, tri-isobutyl boron, trin-hexyl boron, trilauryl boron, di n-butylethyl boron, diisobutyl boronhydride, diethyl boron chloride, diisobutyl boric acid methyl ester anddi n-butyl boric anhydride. Specifically, alkyl radical bonded to boronand having 2 to 4 carbon atoms such as ethyl, n-butyl or isobutyl ismost preferred in practice.

As a manner of using the alkyl boron which is one of the componentsforming the polymerization initiator to be used in the presentinvention, any compound which can produce or liberate theabove-mentioned boron compound in the reaction system can be used. Forexample, in polymerizing an ethylenically unsaturated compound accordingto this invention, if a triethyl boron-ammonia complex, oxygen andhydrogen peroxide are added and then such Lewis acid as hydrochloric oracetic acid is added, said Lewis acid and the ammonia in theabovementioned complex will produce a salt and the triethyl boron willbe liberated and will act as a polymerization initiator together withthe added oxygen and hydrogen peroxide.

As described above, the amount of the alkyl boron used in the presentinvention is 0.001 to 1.0% by weight to the ethylenically unsaturatedcompound to be polymerized and specifically 0.003 to 0.5% by weight isprefable.

Substantially pure oxygen or an oxygen-containing gas, for example, airmay be used in the present invention. The molar ratio of oxygen to theabove-mentioned boron compound used ranges from 0.15/1 to 0.7/ 1,preferably 0.2/1 to 0.5/1. When the molar ratio of the'oxygen to theabove-mentioned boron compound is below 0.15/1 or above 0.7/1, both thereaction velocity and the yield of polymer become less. Therefore,ratios outside said range are not desirable.

The molar ratio of hydrogen peroxide to the abovementioned boroncompound is above 0.3/1 and a ratio in the range of /1 to 0.5/1 isspecifically preferable. Here, if the molar ratio of hydrogen peroxideto the above-mentioned boron compound is below 0.3/1, both the reactionvelocity and the yield of polymer become less and ratios below thisvalue are not desirable.

The molar ratio of hydrogen peroxide to the abovementioned boroncompound may exceed 5/1; however, no commensurate advantage appears toresult.

The ethylenically unsaturated compounds which can be polymerized by themethod of the present invention are represented by the formula:

wherein X X X and X are respectively hydrogen, alkyl, substituted alkyl,alkenyl, halogen, carboxy, aryl, cyano, acyloxy, carboalkyloxy, alkoxyor carbamoyl radicals and can be the same or different.

For example, ethylene, propylene, isobutylene, itaconic acid, allylalcohol, butadiene, vinyl chloride, vinylidene chloride,tetrafiuoroethylene, acrylic acid, styrene, acrylonitrile, vinylacetate, esters of acrylic acid, esters of methacrylic acid, maleicacid, n-butyl vinyl ether and acrylamide are typical examples.

The method of the present invention can be used in homopolymerizing theethylenically unsaturated compounds mentioned above as well as tocopolymerize two or more of said unsaturated compounds. In addition,such ethylenically unsaturated compound can be copolymerized accordingto this invention with any other compound, such as, carbon monoxide,copolymerizable therewith.

The reaction temperature is not specifically limited. Usually atemperature below 200 C. is used. It is very advantageous that themethod of the present invention can be used at comparatively lowtemperatures, such as, 45 C. to 20 C.

In the present invention, the polymerization pressure to be used is notspecifically limited but is properly selected and determined dependingon the kind of the ethylenically unsaturated compound to be polymerizedand the desired composition of the resulting polymer. For example, inthe case of producing polyethylene or a copolymer composed mostly ofethylene, a reaction pressure of about 1000 kg/cm. or higher isadvantageously used. In the case of producing a copolymer of a lowethylene content (usually less than 30% by weight), it is possible touse a reaction pressure below 100 kg./ cm. In the case of polymerizingethylenically unsaturated compounds other than ethylene, a reactionpressure below 15 kg./cm. is usually advantageously used.

In the method of the present invention, any material which will notobstruct the polymerizing reaction may be used as a reaction medium. Inpractice, water is most convenient as a reaction medium. Suspensionpolymerization or emulsion polymerization is preferably used and anyprocess of continuous polymerization, semicontinuous polymerization orbatch polymerization can .be applied.

In the present invention, needless to say, such pH regulators, molecularweight regulators and dispersing agents as are usually used in thepolymerization of the ethylenically unsaturated compounds may beproperly used. Furthermore, the ethylenically unsaturated compound andpolymerization initiator may be properly added during the reaction insuch manner as to regulate the degree of polymerization andpolymerization degree distribution.

The method of the present invention is highly valuable specifically inelevating the polymerization degree of copolymers of ethylene and anyother ethylenically unsaturated compound and in producing high yields ofthe copolymer at a comparatively low reaction pressure as below 100kg./cm. For example, in the conventional method of producing copolymersof ethylene and vinylidene chloride, vinyl chloride, vinyl ester oracrylonitrile, in order to increase the content of the ethylene in thecopolymer, for example, above 15% by weight, at a com paratively lowreaction pressure as below 100 kg./cm. the polymerization degree andyield of polymer will tend to decrease considerably because of theintense degradative monomer chain transfer reaction of ethylene atcomparatively low pressure as below 100 kg./cm. and the use of suchhigher amounts is not practical. However, if the method of the presentinvention is used at a comparatively low temperature, such as, C. to 20C. it is possible to remarkably elevate the polymerization degree andyield of such copolymers even if at a comparatively low reactionpressure as below kg./cm.

Furthermore, when producing a copolymer by combining ethylenicallyunsaturated compounds which are likely to cause degradative monomerchain transfer reactions, such as, allylic compounds, vinyl ether,propylene or isobutylene with vinyl chloride, vinylidene chloride,acrylonitrile or vinyl ester, an increase in the content of the allyliccompound, vinyl ether, propylene or isobutylene in the copolymer,generally the polymerization degree and yield of the copolymer will tendto decrease considerably and the use of such increased amounts is notpractical. However, if the method of the present invention is used at acomparatively low reaction temperature, such as, 45 C. to 20 C., it ispossible to remarkably elevate the polymerization degree and yield ofsuch copolymer.

The method of the present invention will be highly valuable also in suchcases of polymerizing ethylenically unsaturated compounds as:

(l) The case of applying it to a producing process for elevating thecrystallizability of a polymer, for example, in the production of apolyethylene or polyvinyl chloride high in crystallizability, and

(2) The case of applying it to a producing process for reducing thebranches of a polymer, for example, the

production of a linear polyvinyl acetate having few branches.

The following examples are presented:

EXAMPLE 1 Air in a glass-lined autoclave of a capacity of 5 liters wassubstantially completely replaced with deoxidized high purity nitrogen.Then, ion-exchange treated water which was substantially deoxidized bybeing boiled at 100 C. for 30 minutes in a pure nitrogen gas current,vinyl chloride, polyvinyl alcohol (dispersing agent Kurashiki Poval 217(trade name) produced by Kurashiki Rayon Company, Ltd., Japan) andtriisobutyl boron in the respective amounts in the below-mentioned Table1 the reaction was carried out at C. under a reaction pressure shown tobe 36 kg./cm. by gauge for 15 hours.

After the completion of the reaction, the pressure was reduced to normalby removing the residual vinyl chloride and ethylene. The producedslurry was taken out, filtered, washed with water and dried. The yieldof copolymer and compositions (from the chlorine analysis) and thespecific viscosities (as measured at C. as a solution of 0.4%nitro'benzene) of the thus-obtained ethylene-vinyl chloride copolymerswere measured. Further, the odors of the respective copolymers werecompared in the same manner as in Example 1. The results are shown enbloc in- Table 2.

TABLE 2 Oxygen Hydrogen Composition in molar peroxide in 2) (weightpercent) Specific ratio molar ratio Yield Viscosity Odor Remarks TN B 1TN B l in g. Vinyl Ethylene chloride Experiment Nn.:

295 23 .1 16.3 0.37 Cmnpmson' 00 84.0 16.0 0.36 0 030 83.1 16 .9 0.39 No substantial odor-.. Examples of the 875 82.8 17.2 0.39 do presentinven- 805 83 .2 16.8 0.40 ..-do tion. 270 83.6 16.4 0.36 High odorlcjomptifisonf.th 785 83.3 16.6 0 .30 N0 substantial odor-.. e 880 83.116.9 0.38 a0 gion.

1 TNB is an abbreviation of tri n-butyl boron. 1 Trace.

were added to the autoclave. The mixture was kept at 0 EXAMPLE 3 43 C.Oxygen and hydrogen peroxide in the respective amounts mentioned inTable 1 were added thereto and the reaction was carried out at 43 C.under 7 kg./cm. for the times mentioned in Table 1. After the completionof the reaction, the pressure was reduced to normal by removing theresidual vinyl chloride and the produced slurry was taken out, filtered,washed with water liid' dried. The yields of the thus-obtained vinylchloride polymers were measured.

20 g. of a sample of each produced vinyl chloride pol- Air in anautoclave of a capacity of 5 liters made of stainless steel and providedwith a stirrer was substantially completely replaced with deoxidizedhigh purity nitrogen. Then, 2000 cc. of ionexchange treated waterdeoxidized in the same manner as in Example 1 and 1.0 -g. of the samepolyvinyl alcohol as was used in Example 1 as a dispersing agent wereadded to the nitrogen in the autoclave. The ethylenically unsaturatedcompound, boron compound, oxygen and hydrogen peroxide in the amountsymer were tak n and gyl tin maleate and specified in Table 3 were addedthereto. The mixture was 0.8 g. of stearic acid as a lubricant wereadded thereto. kept at the temperature mentioned in Table 3 and the Themixture was kneaded by means of a mixing roll of reaction was carriedout under the pressure mentioned in 3.5 x 8 inches and kept at 180 C.The odors produced Table 3 for 15 hours. After the completion of thereacthen were compared. tion, the pressure was reduced to normal byremoving the TABLE 1 Polyvinyl Yield of the produced Deoxidized alcoholTIB 1 Hydrogen polymer in percent ion- Vinyl (dispersing in percentOxygen peroxide by weight Ex. No. exchange chloride agent) by weight inmolar in molar Odor Remarks water in g. in percent to vinyl ratio toratio to Reaction time in cc. by weight chloride TIB TIB to vinylchloride 5 hrs. 10 hrs. 15 hrs.

2, 000 1, 000 0 .3 0 .020 2, 000 1, 000 0.3 0 .020 1 3 5 No substantialodor-.. 2,000 1,000 0.3 0.020 2 0 9 do 2,000 1,000 0.3 0.020 0.30 7 1726 Slight odor- 2,000 1,000 0.3 0.020 0.60 3 13 18 ..do 2,000 1,000 0.30.200 0.30 22 48 00 High odor 2, 000 1,000 0.3 0.020 0.20 2.0 19 40 Nosubstantial odor... Examples of 2,000 1,000 0.3 0.020 0.30 2.0 25 52 75do the present 2,000 1,000 0.3 0.020 0.50 2.0 13 61 71 do invention.2,000 1,000 0.3 0.020 0.90 2.0 10 24 29 Slight odor Comparison. 2, 0001, 000 0.3 0.020 0.30 0.6 16 35 53 No substantial odor.-. Examples of 2,000 1, 000 0 .3 0 .020 0 .30 4 .0 25 51 77 d the present 2,000 1,000 0.30.030 0.30 2.0 35 71 2 97 invention.

1 TIB in the above table is an abbreviation of triisobutyl boron. 2Hydrogen peroxide in the above table was used in the Ionii of an aqueoussolution of 30%. Trace.

EXAMPLE 2 residual gaseous monomer and the product was taken out,filtered, washed with water and dried. The yield of Air in an autoclaveof a capacity of 5 liters made of stainless steel and provided with astirrer was substantially completely replaced with deoxidized highpurity nitrogen. Then, 2000 cc. of ion-exchange treated watersubstantially completely deoxidized in the same manner as in Example 1,1000 g. of vinyl chloride, 700 g. of ethylene, 1.5 g. of polyvinylalcohol (Kurashiki Poval 217) as a dispersing agent, 3.0 g. of trin-butyl boron and oxygen and hydrogen peroxide in the amounts mentionedin Table 2 were added to the nitrogen in the autoclave and polymer,compositions of the produced polymers (from the carbon and hydrogenanalyses in Experiment No. l and from the chlorine analysis in theothers) and the specific viscosities of said polymers (as measured at 30C. as a toluene solution of 0.4% in Experiment No. 1 and as measured inthe same manner as is mentioned in Example 2 in the others) weremeasured. Further, the odors of the respective copolymers were comparedin the same manner as in Example 1. The results are shown en bloc inTable 3.

TABLE 3 Oxygen Hydrogen Produced Copolymers Experiment in molar peroxidein Tempera- Pressure, Composi- Odor No. Kind Weight Kind Percent ratioto molar ratio ture, C. kgJcm. Yield tion in Speeiiic in g. by wt. BC toBC in g. percent viscosity by wt.

A..." 1, 000 1 1 1% 0.17 0.30 2.0 40 950 2 -{g- 088 0.14 0.30 2.0 as 7905 B 9 0 7.5 4 500 }I 0.01 0.30 2.0 as 20 9/0 }o.3a

1 EC=Ethylenically unsaturated compounds. A=Vinyl acetate. B =Vinylchloride. C=Ethylene. n-butyl boronic acid methyl ester. H=Diisobuty1boron hydride.

What is claimed is:

1. In a method of polymerizing at least one polymerizable ethylenicallyunsaturated compound, that improvement comprising conducting saidpolymerizing in the presence of:

(1) a boron compound represented by the general chemical formula lillIii-R2 Q.

wherein Q is selected from the. class consisting Of R5,

/R3 OB CR and a halogen radical, R R R and R are alkyl radicals and R isselected from the class consisting of an alkyl radical and hydrogenradical, (2) oxygen and (3) hydrogen peroxide, in the respective amountsof 0.001 to 1.0% by weight of said boron compound to said ethylenicallyunsaturated compound, at the molar ratios of oxygen to said boroncompound in the range of 0.15/1 to 0.7/1 and at the molar ratios ofhydrogen peroxide to said boron compound of more than 0.3/1.

2. The improvement claimed in claim 1 wherein said alkyl radicalscontain from 2 to 4 carbon atoms.

3. The improvement claimed in claim 1 wherein the 1 molar ratio ofoxygen to said boron compound is in the range of 0.2/1 to 0.5/1.

4. The improvement claimed in claim 1 wherein the molar ratio ofhydrogen peroxide to said boron compound is in the range of 5/1 to0.5/1.

2 B C Boron compounds.

D =n-butyl vinyl ether.

3 Percent by weight to the total amount of EC.

E Isobutylene. F Diethyl boron chloride. G Di- I= Diisobutyl boronanliydride.

5. The improvement claimed in claim 1 wherein the reaction temperatureis in the range of to 20 C.

6. The improvement claimed in claim 1 wherein said ethylenicallyunsaturated compound is vinyl chloride.

7. The improvement claimed in claim 1 wherein said ethylenicallyunsaturated compound comprises ethylene and any other ethylenicallyunsaturated compound copolymerizable therewith and the reaction pressureis less than kg./cm.

8. The improvement claimed in claim 7 wherein said ethylenicallyunsaturated compounds are ethylene and vinyl chloride.

9. The improvement claimed in claim 1 wherein said ethylenicallyunsaturated compound is ethylene.

10. The improvement in claim 1 wherein said ethylenically unsaturatedcompound comprises vinylacetate and ethylene.

11. The improvement claimed in claim 1 wherein said ethylenicallyunsaturated compound comprises vinyl chloride and n-butyl vinyl ether.

12. The improvement claimed in claim 1 wherein said ethylenicallyunsaturated compound comprises vinyl chloride and isobutylene.

13. The improvement claimed in claim 1 wherein said ethylenicallyunsaturated compound contains 2 to 12 carbon atoms to them'olecule.

References Cited UNITED STATES PATENTS 3,067,185 12/1962 De Coene et al260-92.8 3,112,298 11/1963 Welch 26092.1 3,169,947 2/1965 Stroh et al.26092.8 3,238,186 3/1966 Schultz et al. 26087.5 3,275,611 6/1966 Mottuset al. 26087.3

FOREIGN PATENTS 587,761 8/ 1960 Belgium.

JOSEPH L. SCHOFER, Primary Examiner.

